This application is a 371 of PCT/JP99/0152 filed Mar. 25, 1999.
The present invention relates to an inorganic composite powder with a coating layer comprising two or more inorganic oxides having different refractive indexes respectively and formed on a scaled substrate such as mica and to a cosmetic comprising the inorganic composite powder.
Conventionally a scaled powder such as mica, talc, and sericite has been used for preparing make-up cosmetics such as powder foundation. The effects provided by blending of this scaled powder includes the excellent extendability of the cosmetic on the human skin, improved dispersive property of coloring pigments used therein, and its excellent capability of adhering to the human skin, so that the scaled powder is indispensable in preparation of make-up cosmetics.
These scaled powders as described above generally have a low refractive index of 1.7 or below, and when wet with oily materials blended in a cosmetic, the transparency becomes higher with the capability of covering the human skin as the ground lowered, so that it is required to blend a somewhat large quantity of titanium oxide pigment or the like in the cosmetic to compensate the defects. When a cosmetic with a somewhat large quantity of titanium oxide blended therein is used for making up, the finishing looks like that provided in daubing, which does not satisfy recent preference of users for the natural feeling of appearance.
Japanese Patent Laid-Open Publication No. 282312/1990 discloses a spherical composite powder which easily collapses when pressurized and comprises titanium oxide and silica, and discloses a cosmetic comprising mica powder prepared by coating titanium oxide and then silica thereon.
Further the present inventors proposed in the International Laid-Open Publication WO 92/03119 a composite powder prepared by depositing spherical silica with the size in the order less than a micron on a surface of a scaled substrate to homogeneously scatter light and having the effect of shading the ground. However, as this composite powder comprises silica having the low refractive index and a scaled substrate, when the composite powder is wet by oil mixed in the cosmetic, the transparency becomes higher so that the effect of covering defects on the human skin becomes disadvantageously lower.
Different from this publication, scaled substrates such as barium sulfate have been proposed from a similar view point of homogeneously scattering light, but as their refractive index is high, the requirement for the natural feeling of appearance is not sufficiently satisfied.
Further cosmetics having a satisfactory covering capability for covering such defects as blots and freckles on the human skin and insuring the feeling of transparency are proposed in Japanese Patent Laid-Open Publication No. 56628/1994 and Japanese Patent Laid-Open Publication No. 188723/1996, but these cosmetics are prepared by coating a scaly physiological pigment such mica with titanium oxide or titanium oxide containing a coloring pigment and further laminating a silica layer or a powder having the capability of scattering light thereon, and when laminated with a silica layer, a difference between a refractive index of titanium oxide and that of silica is large, and strong reflection of light occurs on the interface between the two layers, so that the feeling of transparency is not satisfactory.
An object of the present invention is to provide an inorganic composite powder having a satisfactory covering capability and a feeling of transparency. Another object of the present invention is to provide a cosmetic blended with the inorganic composite powder which can cover such defects as blots and freckles on the human skin and insure a natural appearance.
The inorganic composite powder according to the present invention comprises two or more types of inorganic oxides having different refractive indexes respectively and sequentially laminated from the one with the highest refractive index at the bottom on a scaled substrate, wherein the difference in the refractive index between the utmost outer layer and adjoining inner layer is 0.6 or below.
The difference in refractive indexes of all pairs of adjoining two inorganic oxide layers is preferably 0.6 or below.
Further the inorganic composite powder according to the present invention comprises two or more types of inorganic oxides having different refractive indexes respectively and sequentially laminated from the one with the highest refractive index at the bottom on a scaled substrate, wherein a thickness of at least one of the second or higher inorganic oxide layers is within xc2x120% of the value d given by the equation:
d=(xcexxc3x97X/4)/n
wherein xcex indicates a wavelength of visual light, X indicates an odd integer, and n indicates a refractive index of the inorganic oxide.
Said scaled substrate comprises preferably at least one of inorganic oxides selected from the group consisting of natural minerals such as mica, talc, and sericite; synthetic mica, synthetic sericite, plate-formed titanium oxide, plate-formed silica, plate-formed aluminum oxide, boron nitride, barium sulfate, and plate-formed titania and silica composite oxide.
The cosmetic according to the present invention is characterized in that said inorganic composite powder is blended therein and, the refractive index of the inorganic oxide used for forming the utmost outer layer of said inorganic composite powder is preferably 1.5 or below.
Preferred embodiments of the present invention are described below.
A scaled substrate used in the present invention should preferably has an average particle diameter in the range from 2 to 20 xcexcm and a thickness in the range from 0.05 to 1 xcexcm. As the scaled substrate as described above, there can be enumerated such inorganic compounds as natural or synthetic mica, talc, sericite, and further plate-formed titanium oxide, plate-formed silica, plate-formed aluminum oxide, boron nitride, plate-formed barium sulfate, plate-formed titania silica composite oxide, but any other materials may be used so far as the materials have the size as described above.
The inorganic oxides which maybe used for coating the scaled substrate and refractive indexes are shown below.
Titanium oxide (2.50)
Zinc oxide (2.0)
Zirconium oxide (2.2)
Cerium oxide (2.2)
Tin oxide (2.0)
Thallium oxide (2.1)
Barium titanate (2.4)
Aluminum oxide (1.73)
Magnesium oxide (1.77)
Yttrium oxide (1.92)
Silica (1.45)
Magnesium fluoride (1.38)
magnesium carbonate (1.5)
Calcium fluoride (1.43)
In addition, a mixture of these inorganic oxides and an inorganic oxide which is a composite or a solid solution may be used for this purpose.
The inorganic composite powder according to the present invention is formed by laminating thereon two or more inorganic oxides having different refractive indexes respectively selected from those listed above from the one having a higher refractive index into two or more layers. The inorganic oxide is selected based on the covering capability required for the inorganic composite powder to be laminated therewith. To obtain an inorganic composite powder with the higher covering capability, it is preferable to use an inorganic oxide with higher refractive index such as, for instance, titanium oxide for forming the first layer. To obtain an inorganic composite powder with the lower covering capability, it is preferable to use an inorganic oxide with the intermediate covering capability such as aluminum oxide for forming the first layer.
Then, the second and higher layers are formed for lamination, and to suppress reflection of light and obtain the feeling of transparency, it is necessary that the difference of a refractive index of the inorganic oxide used for forming the utmost external layer and that of an inorganic oxide used for forming the adjoining inner layer is less than 0.6. The difference between the refractive indexes should preferably be in the range from 0.05 to 0.5.
In this invention, to further suppress reflection of light and obtain the more excellent feeling of transparency, it is desired to limit a difference between refractive indexes of adjoining layers to 0.6 or below, and. preferably to limit the difference in the range from 0.05 to 0.5. Namely, as the second layer, it is desirable to select an inorganic oxide with the refractive index different by 0.6 or less from a refractive index of the inorganic oxide used for forming the first layer, and selection of inorganic oxides for the third or higher layers should be made based on the same principle. The smaller the difference between refractive indexes of inorganic oxides used for forming the successive layers, the more ideal lamination coating can be obtained, which in turn makes it possible to obtain an inorganic composite powder which does not reflect light and has the more excellent feeling of transparency.
Even if the difference of refractive indexes between two adjoining layers in the inorganic composite powder according to the present invention is not less than 0.6, the configuration is allowable on the condition that the thickness of one of the second and higher layers is within xc2x120% of the value d calculated through the following equation:
d=(xcexxc3x97X/4)/n
wherein xcex indicates a wave length of visual light, X indicates an odd integer, and n indicates a refractive index of the inorganic oxide.
This configuration is employed because a phase of light reflected from a layer just below the one layer and a phase of light reflected from the one layer are reverse to each other and reflection of light is suppressed due to interference between the lights, and the feeling of transparency is provided.
A value in the range from 380 to 780 nm is generally employed as the wave length xcex of the visual light. For instance, to effectively weaken the reflected light in the entire wave length range of visual light, it is preferable to employ the value of 550 nm which is close to the average value of the wave lengths of visual light. Further a wave length used for the equation above can be selected based on considerations to a wave length to be reflected or that to be weakened according to a purpose in use of a cosmetic such as a preferred tone or color as well as to environment for use such as use during daytime or in evening, illumination, and colors of a costume or the like, and at the same time the thickness of a layer can be adjusted.
As a value of the integer X which is an odd number, it is generally preferable to use 1 because the thickness of a layer can be made smaller. For instance, when aluminum oxide is laminated on a layer of titanium oxide, xcex is 550 nm, and n is 1.73, so that the thickness of the aluminum oxide layer is around 80 nm.
Any method known in the art such as that in which a metal salt as a precursor of the inorganic oxide selected as described above is hydrolyzed or a prespecified quantity of an organic metal compound is hydrolyzed in alcohol medium and the hydrolytes are precipitated on a substrate or a substrate with a coating layer formed thereon may be employed for laminating an inorganic oxide.
For instance, a titanium oxide coating layer having the prespecified thickness can be obtained by dispersing a scaled substrate in water, and adding a prespecified quantity of metal salt such as titanyl sulfate into the solution for hydrolysis under alkaline atmosphere to have hydrolyte of the metal salt precipitated on a surface of the scaled substrate.
When laminating silica to form an utmost outer layer, the silica coating layer with a prespecified thickness can be formed, for instance, by adding a prespecified quantity of aqueous solution of alkali metal silicate or a prespecified quantity of organic silicon compound or the like into a dispersion of a scaled substrate with a coating layer having a higher refractive index than silica formed thereon , and further adding an acid or an alkali according to the necessity to have a silicate polymer (hydrolyzed condensate/polymer) deposited on a surface of the scaled substrate with the coating layer or layers having been formed thereon. It is noted that any other method may be employed for forming a silica coating layer.
In the present invention, the thickness of a coating film made from an inorganic oxide can be calculated from a geometrical surface area of a scaled substrate or that with an inorganic oxide coated thereon or a specific surface area measured, for instance, by means of the nitrogen adsorption method, and from a density of the inorganic oxide to be coated thereon. Further, the prespecified quantities of metal salt and organic metal compounds can be calculated from a quantity of the metal oxide to be formed thereon with the prespecified thickness.
In the present invention, it is possible to adjust the covering capability and the feeling of transparency by changing a refractive index of an inorganic oxide to be used for coating and the film thickness, which means that it is possible to adjust the covering capability and the feeling of transparency by selecting an appropriate inorganic oxide to be used for coating and its quantity. If a laminated coating film in which a difference of refractive indexes between adjoining layers is small and the refractive index of each layer becomes gradually smaller toward the utmost outer layer is obtained, a scaled inorganic composite powder reflecting light little and having the feeling of transparency and high covering capability can be obtained regardless of the thickness of the coating layer.
There is no specific limitation concerning the quantity of all inorganic oxides used for coating, but the quantity should preferably be in the range from 1 to 70 weight portions against 100 weight portions of the scaled substrate, and more preferably be in the range from 5 to 50 weight portions. If the quantity is less than 1 weight portion, the sufficient covering capability can hardly be obtained, and if the quantity is over 70 weight portions, the covering capability is too strong to insure the natural finishing, and the film thickness is too large to give comfortable feeling to the users.
With the inorganic composite powder according to the present invention, reflection of light on a surface of the scaled substrate is suppressed with the covering capability improved, so that defects of the human skin as the ground can be hid while insuring the feeling of transparency. Therefore, an inorganic composite powder having the sufficient covering capability and the feeling of transparency can be obtained.
A cosmetic according to the present invention is described below.
Although the cosmetic according to the present invention comprises the inorganic composite powder according to the present invention as described above, the cosmetic gives the feeling of transparency and can hide defects on the ground, so that it can cover the human skin without giving any damage to the natural appearance.
As for the inorganic composite powder to be blended in the cosmetic, it is preferable to use an inorganic oxide with the refractive index of 1.5 or less, and more preferably in the range from1.5 to 1.35 for forming the utmost outer layer of the inorganic composite powder. This configuration is preferable because the refractive index of oil blended in the cosmetic is less than 1.5 and the refractive indexes of the oil and inorganic oxide are close to each other with reflection of light suppressed. The most preferable inorganic oxide used for forming the utmost outer layer is silica.
A quantity of the inorganic composite powder blended in the cosmetic according to the present invention should preferably be in the range from 1 to 90 weight percent. When the percentage is less than 1 weight %, the excellent effect can not be obtained by blending the inorganic oxide in the cosmetic, and when the percentage is more than 90 weight %, such factors as the coloring performance and oily feeling originally required for cosmetics are lost.
A surface of the inorganic composite powder according to the present invention may be processed with silicone or any fluorine compound or the like when blended in a cosmetic.
The cosmetic according to the present invention includes at least one of various components included in ordinary cosmetics including, for instance, heavy aliphatic alcohol; heavy aliphatic acids; oils such as ester oil, paraffin oil, and wax; alcohol such as ethylalcohol, propyleneglycol, sorbitol, and glycerin; moisturizing agents such as mucopolysaccharides, collagens, PCA salt, and lactates; various types of nonion-based, cation-based, anion-based, or amphoteric surface surfactants; gums such as Arabian gum, xanthane gum, polyvinyl pyrrolidone, ethylcellulose, carboxylmethylcellulose, carboxyvinyl polymer, and denatured or not-denatured clay minerals; solvents such as ethylacetate, acetone, toluene; inorganic pigments/dyes; organic pigments/dyes; BHT; chelating agents; and perfumes. Also at least one or more of inorganic fillers such as silica, talc, kaolin, mica, physiological pigments, and various types of organic resins may be included.
The cosmetic according to the present invention can be manufactured in the normal way, and may be used in various forms such as powder form, cake-like form, pencil-like form, stick form, liquid form, and cream-like form. More specifically the cosmetic includes foundation, cream, emulsion, eye-shadow, nail enamel, eye liner, mascara, lip stick, pack, and cosmetic water.
The cosmetic according to the present invention provides the advantage that it is possible to obtain a cosmetic which can cover such defects as wrinkles, blots and melasma on human skin without losing the natural appearance.
The present invention is described in detail below with reference to the examples.